All conventional folding chairs are of one-direction folding and unfolding type having only one seat surface which can be made of rattan, wood, foam rubber, or sponge, etc. Since the two former materials exhibit better ventilation qualities, they are preferred for making chair seats for summer time use. Since the latter two materials exhibit warming qualities, they are preferred for making chair seats for winter time use. Once a conventional folding chair is manufactured, its use is fixed for either summer time use or winter time use. In other words, its use is limited and is unable to meet the requirements in an area having different seasonal modes.